The Perifit is designed for 1000 training sessions of 10 minutes.
So, you are good to use Perifit for at least 5 years if you use it 3 times a week.
The battery is guaranteed for 5 years.
If the battery is flat before the end of the first 5 years, you will get an immediate replacement of your Perifit.
If the battery is dead after 5 years, you will have access to the replacement program which will allow you to obtain a new Perifit sensor for $50 or 45€.